Fix Windows build.

GlobalMemoryStatusEx actually requires _WIN32_WINNT to be defined as
0x0501 (Windows XP) for availability.

For completeness, I bumped WIN32_WINNT in Ticker and OSThreads as well.

Signed-off-by: Austin Seipp <austin@well-typed.com>
Untabify and delete trailing whitespace.

Signed-off-by: Austin Seipp <austin@well-typed.com>
Release note blurb for stack size changes.

Signed-off-by: Austin Seipp <austin@well-typed.com>